/**
 * 终止promise链条 : 返回一个 pending状态的promise
 * 
 *      promiseState:   pending
 *                      fulfilled
 *                      rejected
 */

let p = new Promise((resolve,reject)=>{
    resolve('ok');
})

p.then(value=>{
    console.log(value);
    return new Promise(()=>{});
}).then(value=>{
    console.log(value);
})
